1. Field of the Invention
The present invention relates generally to compositions and processes for cleaning engineering plastic surfaces, and, more particularly, to such compositions that are substantially or entirely free from phosphate and have a reduced mild steel equipment etch.
2. Background Art
Numerous compositions and processes for cleaning plastic surfaces are currently known in the art. Most of them include acid, surfactant(s), and phosphates. In some locations, however, phosphates are forbidden or severely limited to avoid potential pollution and eutrophication of bodies of water that receive discharges of industrial waste water. Thus, compositions that contain little or no phosphate but are still effective cleaners have been sought.
Among the known cleaning compositions containing phosphates, there is a composition that contains phosphoric acid, citric acid, and esters of phosphoric acid together with alkylaminopolyglycol ether surfactant and sufficient basic constituents to result in a pH of about 2. There is also a phosphate-containing cleaner for removing mold that comprises peroxides, phosphoric acid or phosphate salts, divalent cations, and lower carboxylic acids or salts thereof. Citric acid and citrates may constitute the latter ingredient. An aqueous emulsifier composition containing phosphates for cleaning metal surfaces is also known. The emulsifier composition contains oxyethylated alcohol; mono-, di-, or triethylamino carbonate; disodium mono-, di-, or triethylamino ethylenediaminetetraacetate or sodium tripolyphosphate; sodium citrate; and water. Finally, there is a composition containing citric acid, a phosphate salt, a wetting agent, and a corrosion inhibitor that is useful for cleaning metal or plastic surfaces from corrosive etching solutions or their reaction products.
Among the known plastic cleaning solutions is a cleaner for fiber reinforced plastic moldings which is improved by adding to the “usual” ingredients, such as surfactant(s) and organic solvent(s), a carboxylic and/or hydroxycarboxylic acid, which may be citric acid. A known spray cleaning composition for plastic articles includes water insoluble inorganic powder and conventional surfactants and may also contain builders, defoaming agents, chelating agent, and solvent. Citric acid is taught as an example of a chelating agent. A detergent composition recommended for cleaning plastic sheets used in horticulture contains polyoxyethylene alkyl ether (a nonionic surfactant) and sodium citrate as its main components. Another composition for cleaning metal, plastic, or glass includes lithium salts of an acidic partial ester of sulfuric acid, of a sulfonic acid, or of an alkanolamine with citric acid as an optional ingredient.
Compositions containing a weak organic acid and an acrylic polymer have been used to clean semipermeable membranes, such as cellulose acetate and triacetate, polyamide, and polysulfone membranes. Preferred weak acids for this membrane cleaning application include citric acid, malic acid, sulfamic acid, and mixtures thereof. Another known acid-containing composition is used for cleaning ceramic cladding materials. This composition includes citric acid and partially hydrogenated caprolactam oligomers.
Finally, liquid detergent compositions containing surfactants are known. The surfactant acts function to retard redeposition of soil. Furthermore, these detergent compositions may include a water soluble sequestrant builder that may be or include citrates.